Not Applicable
1. Field of the Invention
The present disclosure is related generally to bulk product conveying machinery and methods including means to permit movement of a conveyor to different working positions or orientations relative to the carrier on which it is mounted. More particularly, the apparatus is related to portable aggregate handling conveyors wherein the conveyor can be telescoped to a more compact configuration than it has when operating to facilitate transporting the conveyor along a highway. In greater particularity, the invention is related to an apparatus including separate conveyors mounted on a single carrier so that they successively convey a load to multiple discharge points to effect the formation of larger stockpiles than is otherwise possible and to reduce the segregation of stored material by size during the stacking process.
In particular, the apparatus according to this specification is related to an endless belt-type conveyor having means for telescopically varying its conveying length either manually or automatically.
2. Description of Related Art
Radial stacking conveyors are known in the art. For example, U.S. Pat. No. 5,515,961 to Murphy and Schmidgall discloses a portable radial stacking conveyor that may be easily folded from its fully extended length of approximately 38.1 m (125 feet) to a transport configuration of slightly more than half the fully extended length. Radial stacking of bulk materials such as aggregate for road construction, grain, or coal enables substantially more material to be stored in a stack than is possible using a conventional, conical stack.
A telescoping, variable length conveyor assembly is disclosed by Thompson in U.S. Pat. No. 4,474,287 issued Oct. 2, 1984, for a variable length conveyor assembly. Thompson""s conveyor is intended for use in coal mines to remove coal from a continuous mining machine. Another telescoping mining tool is disclosed in U.S. Pat. No. 4,236,630 issued Dec. 2, 1980 to Sander, et al. for an extensible telescopic coal bunker for subsurface mining. Neither unit is adapted for radial stacking. A similar telescopic belt conveyor is shown in U.S. Pat. No. 4,643,299 issued Feb. 17, 1987, to Calundan for a conveyor that uses a complex serpentine belt path to keep the single belt at the correct tension, regardless of the degree of extension of the discharge end from the feed end.
Another approach is shown by Smith in U.S. Pat. No. 4,523,669 issued Jun. 18, 1985, for a retractable conveyor belt that can include an optional articulated conveyor element on the discharge end of the main, vehicle-mounted conveyor. U.S. Pat. No. 4,624,357 issued Nov. 25, 1986 to Oury et al. for a vehicle-mounted extensible conveyor also describes a portable conveyor that can be extended and retracted in addition to being pivoted both vertically and laterally to discharge material at the desired point. Both of these vehicle-mounted conveyor assemblies are intended for transporting wet concrete from the mixer truck to the pour location. Neither is suited for stacking large piles of aggregate that are needed in the road construction industry.
Several other radial stacking conveyors have been developed by earlier workers in the field. Among those patented are: U.S. Pat. No. 5,390,777 issued Feb. 21, 1995, to Gage for a constant pivot mechanism for variable height radial stacking conveyors; U.S. Pat. No. 4,427,104 issued Jan. 24, 1984 to Reid, Jr. for a radial stacker, and; U.S. Pat. No. 4,245,732 issued Jan. 20, 1981 to Couperus for a compactly foldable radial luffing stacker. None of the radial stackers shown by Gage, Reid, and Couperus disclose extending, telescoping or other means for varying the radius at which material is deposited.
A method and apparatus for accumulating stockpiles of flowable solid material is disclosed by Ryan in U.S. Pat. No. 4,744,459 issued Mar. 17, 1988. Ryan""s method includes depositing the material in staggered piles to achieve satisfactory intermixing of the stockpiled materials. The apparatus is intended, however, for use inside buildings and appears to be neither portable nor easily re-locatable.
None of the radial stackers known in the art provide either the maximum storage capacity or the maximum efficiency that could be obtained from a portable radial stacking conveyor. By way of example, a portable telescopic radial stacker that is manufactured by Thor Aggregate Equipment of 839 Westport Crescent, Mississauga, Ontario, L5T 1E7, Canada has a full extension length of about 136 ft. Thor states that its telescopic stacker will stockpile 154% of the material that could be placed using a conventional radial stacker of the same length. The extra material is stacked radially closer to the center, or pivot point, of the arc described by the discharge end of the radial stacking conveyor as it places material for storage.
An article in the July/August, 1998 Aggregates and Roadbuilding Contractor magazine by Stephen R. Carr identified several limitations inherent in conventional means for radial stacking that may be overcome with telescoping radial stackers. When materials having a distribution of particle sizes are delivered to a stockpile, the particles tend to segregate according to size. Larger particles tend to roll to the bottom of a stack. A conical stack made with evenly mixed material will tend to form with smaller particles being concentrated in the center and top of the stack and larger particles at the bottom and outside of the stack. Those tendencies increase with increasing stack height. The same forces apply to a radial stack with larger particles concentrating at the outer bottom edge of the stockpile. In some instances it is necessary to re-build a stockpile by re-distributing the material with loaders and bulldozers.
When used properly, the telescoping radial stacker will stockpile product without segregating the screened material according to size and deviate from specification. The even distribution of the particles is maintained by stockpiling the material in layers of small stacks instead of one large stack. Not only does the telescoping action minimize size segregation, it also enables the operator to store a substantially larger amount of material in a stockpile of any given radius by filling part of the interior of the stacker arc with material.
In evaluating whether to purchase a conventional stacker, a radial stacker, or a telescopic radial stacker, the costs that must be paid as the result of operating each model should be the considered. Consequences of stockpile size segregation can add considerably to the cost of operating either a radial stacker, which is less expensive than a telescopic radial stacker, or a relatively inexpensive fixed stacker.
An operator supplying aggregate may be required to pay a penalty for delivering non-conforming product. To avoid such penalties, it may be necessary to operate bulldozers, scrapers, dump trucks, loaders, and other machinery for extended periods to reform a segregated stockpile; not only is such machinery expensive to operate, it also compacts, and reduces the value of, the product. A loader may use more operator time, 15 or 20% more fuel, and extra machine wear and tear loading out a compacted aggregate pile compared to a stockpile created by a conveyor.
Other costs of re-blending product can include the reduced availability of machines for revenue-producing tasks, the value of foregone opportunity, and the necessity of purchasing, maintaining, depreciating, and financing additional equipment to replace the equipment engaged in stockpile re-work. The additional work entailed to re-blend aggregate will also increase labor costs. Even if the degree of segregation is not so severe that it must be re-built, more time and more skill will be required if the loader operator must take material from different locations of the pile in order to create, in each truckload, a batch of aggregate that conforms to the applicable specifications.
Not only is it important to be able to control the location of the conveyor discharge, aggregate stacking machinery must frequently be portable so that the owner of the equipment may relocate to the vicinity of the road improvements that are undertaken. Although many road construction contractors have a statewide or regional area in which most or all of their work is done, it can still be necessary to relocate from one site to another site that is several hundred miles away. In other instances, it is necessary to relocate the field operations of a road construction enterprise fairly frequently, perhaps monthly or even more often. In either circumstance, preferred characteristics of portable aggregate handling equipment generally, and of portable telescoping radial stacking conveyors specifically, include:
The equipment can be towed from one job site to the next over state and federal highways in compliance with routinely granted oversize load permits.
The equipment converts from the transport configuration to the working configuration both quickly and easily.
The transport configuration provides dual-wheeled tandem axles so that transport permits may be obtained in most or all states.
The radial stacking configuration has adequately spaced-apart travel wheels to maximize stability.
The equipment produces that maximum extension length that is practical in a portable stacking conveyor.
None of the known telescoping radial stacking conveyors adequately incorporates all of the desirable features identified above. In addition, no prior art portable telescopic radial stacker is known to have an overall operating length of more than 41.5 m (136 feet). Increasing conveyor length by only 4.3 m (14 feet) yields a conveyor that is 45.7 m (150 feet) long that makes a stockpile that holds over 30% more material. In other words, a telescoping radial stacker that has a length of 45.7 m (150 feet) can both prevent aggregate segregation problems and also create a stockpile that holds approximately twice as much material as a stockpile made using a conventional (non-telescoping) radial stacker that is 41.5 m (136 feet) long.
The lengths to which the stinger extends and retracts are limited by several practical constraints.
Portability is an essential feature of radial stackers of this type, and the ease or difficulty with which a machine can be relocated is an important consideration for the owner of such machines. The maximum vehicle length permitted for transport over public roadways varies by jurisdiction. In practical terms, however, a towing length of less than 24.4 m (80 feet) is desirable in most jurisdictions, and the maximum height must not exceed 4.3 m (14 feet).
Another important consideration is the maximum extension length of the conveyor. Adding only a few meters (feet) to the working length of a conveyor will substantially increases the capacity of the stockpile that the conveyor can make. It can readily be appreciated that each additional meter of extension can add many tons to the total amount of material in the stockpile by increasing both the radius and the height of the stockpile. Filling more of the interior radius of the stockpile is of less benefit because the amount potential additional storage volume is much less due to the fact that the radius of the open area at the center of the stockpile cannot be less than the radius traveled by the stacker radial wheels.
The constraints mentioned above make it difficult to fabricate a portable telescoping radial stacking conveyor with an extension much greater than 45.7 m (150 feet). The requirement of transportability on public roads limits the height and the length of the primary conveyor framework, the exterior of the secondary framework must be smaller in length, width, and height than the interior of the primary. The secondary and primary frames must overlap. In the present embodiment, an overlap of about 12 feet is provided. An economically feasible way to reduce overlap substantially from about 12 feet does not appear forthcoming. Yet another constraint on the maximum conveyor extension is the necessity of supporting the conveyor by only the ground-contacting wheels and pivot. Extension of a stinger beyond the distance for which the entire system has been designed could cause the machine to tip or result in failure of the frame members or support struts.
These limitations persist regardless of the configuration of the primary or xe2x80x9cmainxe2x80x9d and the retractable secondary, or xe2x80x9cstingerxe2x80x9d conveyors. The longest prior art telescoping portable radial stacker known is believed to have approximately the same transport length as an embodiment of the present disclosure but with a shorter operational length of 41.5 m (136 feet). That manufacturer states that the telescopic conveyor can stockpile 50% more material than a conventional (non-telescoping) conveyor of an equal fixed length (i.e. 41.5 m (136 feet)). The extra material is stacked radially closer to the center, or pivot point, of the arc described by the discharge end of the stacker that is 41.5 m (136 feet) in length and can pile approximately 340,200 kg (375 tons) per degree of arc. The structure disclosed is designed to provide a maximum extension of 45.7 m (150 feet) which makes it possible to stockpile 453,600 kg (500 tons) of aggregate per degree of arc. By practicing the present disclosure, it is possible to stockpile nearly 30% more material than can be handled by any other radial stacking conveyor presently known.
It should be emphasized that there are several advantages to be gained from increasing the storage capacity of a bulk product stockpile. A single machine set-up (or fewer set-ups in the case of very large projects) enhances production because more time is spent doing productive work and less time is spent in preparation. When the area required for storage is smaller, the cost of land is lower. With less area disturbed, there is less fugitive dust emitted and restoration of the land to prepare it for another purpose is effected more easily and at less expense.
What is needed, then, is a radial stacking conveyor that maximizes the amount of material that can be placed and that can be quickly relocated from one job site to another. The industry further needs a portable radial stacking conveyor that has a telescoping discharge and can be controlled to pile bulk materials such as aggregate in layers of small piles so that the material does not segregate based on particle size.
The telescoping portable radial stacker according to the present disclosure overcomes some limitations and minimizes the impact of others. Portability is achieved by withdrawing the stinger into the main conveyor frame to reduce the towing length of 24.4 m (80 feet) while holding the maximum height to 4.2 m (13xe2x80x2-10xe2x80x3).
This disclosure shows a telescoping portable radial stacking conveyor that may be converted from the transport configuration to the working configuration both quickly and easily. Product stockpiled with such an embodiment has less segregation than product stockpiled using conventional techniques. This apparatus is designed to maintain the quality of the stockpiled product so that material that meets specification when delivered to the stacker will also meet the specification when it is reclaimed from the stockpile. The enhanced efficiency of the present stacker compared to earlier attempts of others is gained by the ability to store more material in better condition than any other portable stacking system known. The proper storage technique can reduce re-work and make the ordinary activity of product loading much more easily accomplished.
The ability to form large stockpiles relatively quickly increases the efficiency of crushing plant operations. The present invention can be made with various belt widths. Configurations that use a 91 cm (36xe2x80x3) belt width are frequently specified. Equipped with electric belt drive motors having adequate horsepower on both the primary and the secondary conveyors, the stacker can place about 907,200 kg (1,000 tons) of crushed rock aggregate per hour.
The telescoping radial stacker is comprised of a radial stacking conveyor to which is added an axially extensible, retractable stinger conveyor and a control system to enable the position of the stinger to be changed periodically (e.g. every minute or two). The control system can cause the stinger to reciprocate automatically or it may enable the operator to manually position the discharge point of the stinger.
The invention is an improved portable radial stacking conveyor that has a telescoping discharge portion. The telescoping discharge portion is a second, relatively smaller, belt conveyor, often referred to as the stinger. The stinger fits within the framework of the primary, or main, conveyor so that the upper belt surface of the stinger conveyor belt is below the return idler rolls of the primary conveyor. Material discharged from the primary belt lands on the stinger belt rather than falling directly onto the stockpile. Separate drive mechanisms are provided for the stinger conveyor belt and for the main conveyor belt. Each conveyor belt is driven by an electric motor and gear reducer assembly mounted at the discharge end that turns the shaft of the end roller which has nearly 180 degree contact with the inner side of the belt.
The stinger is mounted on rollers so that it can extend longitudinally from within the primary conveyor framework or be retracted into the primary conveyor. Main conveyor and stinger longitudinal axes are parallel, and the stinger is equipped with a positioner drive mechanism to extend and retract it axially with respect to the main conveyor structure. Extending or retracting the stinger changes the effective length of the conveyor and the location at which product will be deposited. Proper deposition of product greatly reduces segregation of large from small particles. In the present embodiment, the maximum extension is about 45.7 m (150 feet) which enables an operator to prepare a stockpile that is 15.2 m (50 feet) tall.
Automatic controls can be used to effect both axial movement of the stinger and radial movement of the main conveyor. Alternatively, the machine operator may set the discharge position manually.
The present stacking conveyor is made of two truss sections, a larger, outer steel framework into which the smaller, inner, moveable stinger truss section fits. The larger section, or outer framework, is mounted to an axle assembly that has at least one ground-contacting wheel and tire mounted on either side of the longitudinal axis of the outer frame. The axle assembly may also include radial movement wheels that may be the same as the road transport wheels, but are preferably different so that the appropriate flotation can be obtained and also so that the wheels can be quickly set-up using hydraulic or mechanical provisions to transfer the weight from the transport wheels to the radial motion wheels. Another important feature is that the preferred transport carriage includes road wheels that are carried on true tandem walking beam axles that, compared to conventional tandem axles, provide not only superior weight distribution on road surfaces, but also greatly enhanced ride performance and better flotation. Dual wheeled tandem axles make it easier to obtain transport permits that most states require when loads that are as wide and as heavy as the present invention travel over public roads. Some jurisdictions will not permit transport of a load the size and weight of a portable telescoping radial stacking conveyor unless the trailing vehicle is fitted with tandem axles.
An elevating mechanism, or telescoping undercarriage, is provided to control the material discharge height. A variety of elevating mechanisms may be used and may be mechanical or hydraulic. Although a single ram may be used to raise and lower the conveyor, a satisfactory configuration may use two hydraulic rams. On each (the left and the right) side of the machine, an elevating ram may be disposed between a lower edge of the outer frame and a location near the corresponding axle assembly or other part of the undercarriage framework that is supported by the radial travel wheels. Extending the hydraulic elevating rams raises the discharge end of the conveyor and allows the system to accommodate the increasing height of the stockpile. Special attention to the elevating rams is warranted. Conventional radial stackers can engage supports such as telescoping support arms at various convenient heights using pins or other fasteners that will inhibit lateral sway; conventional stackers, however, do not require elevation changes every few minutes. Any of several techniques may be used to prevent hydraulic fluid from flowing freely between the two cylinders to de-stabilize the system with possible catastrophic failure. Separate synchronizable pumps may be fitted to each ram. Normally closed power operated stop valves may be situated at the discharge of each cylinder to prevent fluid from flowing except when the valves are opened by the operator to adjust the height. Other techniques may include a system of check valves which may be augmented by pressure regulators to control the release of hydraulic fluid.
The feed end of the conveyor is supported by a pivot plate set onto a suitable flat area of the ground. A counterweight that weighs about 12,000 pounds keeps the stacker feed end in contact with the ground-mounted pivot plate, even when the belts are filled with product. The pivot plate may be fitted with suitable polymer pads or strips to reduce friction as the machine pivots. The counterweight allows the radial travel wheels to be located closer to the pivot point than would otherwise be possible. The small radius described by the radial travel wheels reduces the amount of space which must be kept free of stockpiled product and increases the area available for product storage. This increased storage capacity significantly enhances the efficiency of the storage system.
Several factors contribute to the ability of the machine to reach farther than does the usual telescopic conveyor. First, the integrity of the telescoping portion, or stinger is maximized by careful design. Where it is advantageous to do so, particularly with the bottom chord which is in compression, the structural members are made from rectangular tubing rather than the angle stock that is conventionally used. Advantages obtained with the technique include: there is much less build-up of material and resulting increase to dead weight; the machine stays cleaner, and the structure is more resistant to buckling. The top chord, however, may be formed satisfactorily from angle stock. Also, it may be desirable to vary the thickness or other dimensions of the structural members over their length. For example, the top chord may be made using 10.2 cmxc3x9715.2 cm (4xe2x80x3xc3x976xe2x80x3) angle for the first 12.2 m (40 feet) and 10.2 cmxc3x9710.2 cm (4xe2x80x3xc3x974xe2x80x3) stock for the second 12.2 m (40 feet) of length. The bottom chord may be made from 10.2 cmxc3x9715.2 cmxc3x9712.7 mm (4xe2x80x3xc3x976xe2x80x3xc3x97xc2xdxe2x80x3) wall rectangular tubing for the first (innermost) 6.1 m (20 feet) with the wall thickness reducing to 9.5 mm (xe2x85x9cxe2x80x3) for the second 6.1 m (20 feet), to 6.4 mm (xc2xcxe2x80x3) for the third 6.1 m (20 feet) and to a 4.8 mm ({fraction (3/16)}xe2x80x3) wall for the final 6.1 m (20 feet).
Another feature of the stinger is a design in which all of the heaviest compression loads are carried by the shorter, more rigid, lattice members of the Pratt trusses. The heaviest compression loads occur in the region between the primary truss rollers and the secondary truss rollers. This design allows the extension rollers to be situated closer together which increases the overall length of the extended conveyor.
The stinger is fitted with tubular rails that extend laterally from the lower corners of the framework. A pair of tandem walking beam rollers at the discharge end of the outer framework engage the bottom of each stinger rail. A second pair of tandem walking beam rollers engage the top of each rail. The second roller set is situated about 12 feet from the discharge end of the outer framework. Adjustments can be made to the rollers to obtain good performance and to compensate for wear. The reduced overlap of only 12 feet, compared to the 15 to 18 feet that previous conveyors required, allows the reach of the stinger to be extended significantly.
Alignment of the stinger truss is aided by using a mill-finished rectangular tubular rail to carry the stinger along the rollers. The tolerances of the tubing are much more precise than the tolerances that may be obtained practically from a fabricated load-bearing alignment member. Some prior apparatus use rollers on the bottom of the stinger truss and inwardly disposed rollers contacting the top of the stinger truss to hold the stinger as it moves in and out. Another advantage of the rectangular tubing rail is that only the bottom chord of the truss is required to have sufficient strength to withstand the bending loads imposed by the rollers. The result is that the top chord carries only tension loads which makes it possible to use lighter angle materials instead of heavier tubular material. By locating the rails against the sides of the stinger framework, it is possible to make the tandem roller walking beam roller assemblies using high performance flanged track rollers (cam rollers); the roller flanges resist stinger side loads. Each walking beam roller assembly may have a static load capacity of about 100,000 pounds. Not only does the walking beam assembly reduce the effect of surface irregularities and other rail imperfections, the assemblies are fully independent both front-to-back and side-to-side. The independence minimizes the transmission of shock through the members and tends to reduce the effect of cumulative defects.
Another technique that may be incorporated into the various embodiments is to form the secondary conveyor sections with a camber to compensate for the dead weight of the structure. A member that is 24.4 m (80 feet) long may be formed with a 7.6 cm (3xe2x80x3) camber. When extended, the dead weight of the truss assembly will cause enough deflection to make the conveyor section straight. There may be some observable deflection depending upon the angle at which the unit is set and the amount of the live load.
The deflection and the overall weight of the live load that the stinger carries is reduced by reducing the live load. When stacking 907,200 kg (1000 tons) per hour, the main conveyor belt runs at 122 m (400 feet) per minute. The stinger belt, however, runs at 183 m (600 feet) per minute. The faster secondary lowers the material profile and reduces the live load by 33%.
A single hydraulic source is provided that can power jacks that lift the pivot end when connecting the unit to a tractor for re-location, the elevating rams, the radial travel wheel booms, the radial travel drives, and the stinger positioner.
Longitudinal movement of the stinger section is effected by a stinger positioner that is affixed to the lower end of the stinger section. Configuring the stinger winch mechanism on the inside of the stinger itself makes it possible to lengthen the stinger somewhat because there is no requirement to provide space for that winch mechanism at the lower end of the primary frame. The positioning apparatus is comprised of a hydraulic motor and speed-reducing planetary gear set powered winch drum that has a wire rope wound on it.
The winch drum may have two wire ropes attached to it and extending in opposite directions from the winch drum. The other end of each rope would be affixed to opposite ends of the primary conveyor frame so that when the stinger is fully retracted, one end of the retract rope would be connected to the feed end of the primary conveyor and the rope would be fully wound onto the drum with the end affixed to the drum. Although displaced axially along the winch drum by a distance to avoid unnecessary wear, the extend rope would wind onto the drum from the opposite direction at the same radial point from which the retract rope unwinds tangentially from the drum.
In an alternative embodiment, one end of the wire rope is connected to the discharge end of the main conveyor. The other end of the wire rope is connected to the feed end of the main conveyor after several turns of rope have been placed around the winch drum. The hydraulic motor can turn the drum either direction thereby un-winding rope on one side and winding the wire rope on the other side to either retract or extend the stinger. The winding drum may be grooved to receive the wire rope; it may also be practical to fashion the drum with a smooth rope-contacting surface.
A variety of other mechanisms may also be used with equivalent stinger positioning effect. For example, the stinger could be moved by turning one or more screws that extend the length of the primary conveyor. The stinger could be moved by a cogwheel that engages a gear rack extending for the distance of travel. Hydraulic rams could either directly or with suitable blocks and tackle move the stinger. It would also be possible to extend and retract the stinger with a reciprocating pawl attached eccentrically to a rotating gearmotor shaft. The pawl could sequentially engage a linear array of dogs extending substantially the length of the primary conveyor. Reversing could be effected using automatic devices. Other methods for positioning the stinger include use of a chain fall or hoist engaged with a chain that runs from the discharge end of the primary conveyor to the feed end. The winch could alternatively be reeved on parallel xe2x80x9cVxe2x80x9d grooved wheels in a similar manner to that used with electric passenger and freight elevators.
An xe2x80x9cE-chainxe2x80x9d interconnects the primary and secondary conveyor structures. The E-chain holds the flexible hydraulic hoses that power the stinger positioner drive, the electrical power supply cord that powers the conveyor belt drive motor, and the signal leads that connect the zero belt speed sensor and the tilt sensor to a control panel. Although it is known that an E-chain may be conveniently used to retain the hydraulic and electrical lines, any of the several other equivalent means that may include guide rods, screen, cages, armor, etc. may be used as well. The required functionality is primarily to prevent the power and signal lines from becoming damaged through accidental contact with the other moving and fixed parts of the system by confining the movement of the power and signal lines to a plane that is spaced apart from, and parallel to, the axis of stinger movement.
Among the advantages of operating the stinger positioner drive with hydraulic power instead of electric power are the small size and light weight of hydraulic motors, the ability of hydraulic motors to withstand repeated start, run, stop/stall cycles under full load in either direction without being damaged, and the ability to control positions with precision. It is to be understood, however, that electric, pneumatic, and other types of drive systems are equivalent to the hydraulic system of this disclosure. Extending and retracting the stinger may be controlled manually by an operator or automatically by an automatic control system.
One automatic control system uses interval timers to periodically open solenoid-operated hydraulic valves for specific lengths of time so that the stinger will move a specific distance in the desired direction along its longitudinal axis and so that the radial drive wheels will advance the conveyor angularly about the pivot. When the conveyor reaches an end of the arc along which it travels, the elevating mechanism can be activated manually or automatically to raise the discharge end of the conveyor by an appropriate distance; the direction of radial wheel travel will also be reversed.
Another method of controlling the formation of stockpiles is to use a Programmable Logic Controller (PLC). Such a system may set timers to control when and for how long the respective valves should remain open. Alternatively, the PLC may activate motors and positioners in response to input from sensors that respond to changes of the controlled component. It is also possible for the controller to use other information to affect or override various commands and sensed conditions. For example, the system could receive signals from a sensor that detects the presence of material in the feed hopper and the controller could provide that if the feed hopper is empty for 45 seconds, pause all position control timers. The PLC can control many aspects of the stockpile the telescoping radial stacking conveyor makes. Among other things, the PLC can provide instructions that will cause the stacker to form a stockpile that is rectangular rather than arcuate; it can place the stored material in discrete piles, windrows, concentric arcs, or distribute the material to evenly fill an irregular container such as the hold of a ship, or to fill various bulk material containers, barges, rail cars, and other vessels.
Other equivalent positioning systems may be used to control the position of the stinger relative to the main conveyor, to control the height of the primary conveyor discharge, and to control the radial displacement of the stacker by operating the radial travel wheels.
The radial travel wheels may be powered or unpowered. When powered, it is believed preferable to use hydraulic power although other motors, engines, winches, or separate vehicles may be used to move the stacker radially on the pivot.
Various sensors, controls and alarms may be provided to detect and correct out of tolerance positions or responses. For example, a stopped belt sensor is fitted on the stinger belt to prevent the damage that could come from the main belt continuing to deliver material to a stinger that is not in operation. A belt could be ruined and other components could be harmed. When the stinger belt sensor detects that the stinger belt is not moving, it should immediately shut down the primary conveyor.
The stinger positioner drive may be shut off by limit switches mounted at both the inboard and the outboard ends of the stinger travel range. In addition to electrical limit switches, mechanical blocks have been configured to retain the components in the unlikely event of failure of both the electrically operated control and the limit switch systems. By selecting appropriate power and torque ratings for the hydraulic positioner drive motor, mechanical limit blocks could assure that the winch does not over-drive the stinger past the design limit.
A tilt sensor, or high stack sensor, is provided at the discharge end of the stinger to provide enhanced functionality and operational flexibility. The tilt sensor is a position-sensitive switch that depends from the lower end of a short chain or rod that is swingably mounted from a point near the stinger belt discharge. A chain or rod about three feet long is generally satisfactory, but other lengths could be used instead. When the height of the pile approaches the discharge of the stinger conveyor, the accumulating material will impinge on the tilt sensor hanging from the end of the conveyor frame and deflect it angularly. When the amount by which the tilt sensor is deflected from vertical reaches 15 degrees or more, it signals the controller to move the stinger to the next location. In this optional operating mode, the sensor implements the option of moving the conveyor discharge in response to the presence of stockpiled material rather than simply advancing the discharge point incrementally at pre-set time intervals. The advantage of this option is that uniform stockpiles can be made even if the material is delivered to the stacker in uneven surges.
When the system operating mode is set to move the conveyor discharge point after a specific time interval, the sensor may be used as a high stack limit switch to halt the conveyor if the system were unable to move the conveyor discharge to a location where additional material were needed.
Likewise, when the system is operating manually, the tilt sensor may be used as a high stack limit switch to alarm or shut down the system if the operator does not, for any reason, do so.
The belts, troughing rollers, and return idlers are standard sizes and meet all applicable CEMA requirements, guidelines, and standards. It is to be understood that other features may be incorporated into articles made according to this disclosure. For example, it may prove desirable to provide additional telescoping stinger sections. The design of the primary and secondary conveyors is readily adapted to receiving a third conveyor assembly that may be shorter than the secondary conveyor. The interior of each of the conveyor truss sections is clear below the return idlers which provides a region in which a third conveyor section could be mounted within the secondary conveyor in a manner similar to the way the secondary conveyor is mounted inside the primary conveyor.
Although the designs illustrated may be adapted for such use, it is possible that other truss designs and other materials would be used in part or all of a telescoping radial stacking conveyor that has three or more conveyor sections. For example, it may be necessary to fabricate part or all of the structures using specially formulated or specially treated materials to obtain structures of sufficient strength while also keeping the overall weight of the system low enough to be transported over public roadways.